Method for producing a sandwich composite component with pressed two or three-dimensional shape and such a composite component

ABSTRACT

Described is a method for producing a sandwich composite component and a sandwich composite component with a pressed two- or three-dimensional shape, having at least one structured core layer made of thermoplastic material which has two opposite core layer surfaces, each bonded to a thermoplastic cover layer. A sandwich composite component is also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to International Application No. PCT/EP2020/057508,filed Mar. 18, 2020, which claims priority to German Patent ApplicationNo. 10 2019 204 460.3, filed Mar. 29, 2019, the contents of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a method for producing a sandwich compositecomponent with pressed two- or three-dimensional shape, having at leastone structured core layer made of a thermoplastic material, which hastwo opposite core layer surfaces, each of which is directly orindirectly bonded to a thermoplastic cover layer.

Description of the Prior Art

Sandwich composite components are used widely in lightweightconstruction, since they have very high load per unit areacharacteristics and at the same time low specific density. Forstructural components which are subject to heavy loads, these sandwichcomposites typically include structured core layers, in the form of ahoneycomb structure, for example, which is bonded on each side with afiber-reinforced plastic cover layer. Although it is possible tomanufacture large-area, flat sandwich composite components even inlarge-scale production, there are still not enough production methodswith which it is possible to create endless-fiber reinforced sandwichcomposite components in cycle times in the order of minutes and withspecified surface curvatures.

Methods for large-scale production, particularly of endless-fiberreinforced sandwich components with homogeneously foamed corestructures, are very well known, but sandwich composite components witha foamed core have lower specific mechanical rigidities than sandwichcomposite components with a structured core. Furthermore, the process offoaming the core while simultaneously molding the cover layers thatdelimit the core on either side is difficult to control.

Document DE 10 2011 006 819 A1 discloses a method for producing athree-dimensionally contoured sandwich structure having of twothermoplastic cover layers and core layer with a honeycomb structurepositioned between them. In order to achieve the three-dimensionalcontouring of the sandwich structure, the honeycomb-like core layer ispre-processed in a cutting or separating processing method in order toobtain the intended three-dimensional contour. Afterwards, thethermoplastic cover layers are bonded cohesively with the core layer bya process of hot pressing them onto the processed core material. It isquite plain that this approach is only suitable for low volumeproduction or prototype construction.

Document DE 43 23 590 A1 discloses a method for producing athree-dimensionally shaped layer composite component whose core layer offoamed thermoplastic material, which is bonded cohesively withthermoplastic cover layers on both sides. In this process, the corelayer and the cover layers are first arranged in a loose stackconfiguration and then joined in a single hot pressing process. Duringthe hot pressing process, the two cover layers and the core layer eachform a cohesive composite bond.

A method for producing a sandwich panel with a reinforced foam corewhich is similar to the preceding manufacturing method is disclosed inEP 3 263 321 A1. However, in neither of the cases cited above the foamcore does not offer the surface rigidity and surface load-bearingcapacity that is associated with a structured core layer.

Document WO 2013/143569 A1 discloses a manufacturing method for asandwich composite component having a honeycomb core layer and twofiber-reinforced thermoplastic cover layers. The special feature of thedisclosed sandwich component is that the honeycomb core layer is madefrom a cellulose-based material which assumes a correspondinglythree-dimensionally configured component shape under the effects ofpressure and heat as part of a deformation process.

Besides the above, a number of production methods involving processingthermosets for producing sandwich components are known, such as vacuuminfusion, gap impregnation or resin injection methods. However, thecuring reaction of thermosetting plastics during processing and the factthat some process steps are performed manually means they are of limitedbenefit, if not entirely unsuitable for large-scale manufacturing.

Document EP 1 993 808 B1 discloses a method for the production of a3-dimensionally shaped sandwich structure, which is transferred to acompression mold with compression mold stamps that can be deflectedvariably one after the other in order to mould it. The internal corelayer in the sandwich structure is exposed to varying degrees ofcompression in different regions, to such an extent that creases form.

Document EP 1 626 852 B1 discloses a composite component and a methodfor production thereof, wherein the component is shapedtwo-dimensionally in the manner of a deep-drawing method and athermoplastic material enclosing the periphery thereof is joined to itby compression.

Document DE 10 2012 002 559 A1 discloses a tool for manufacturing asandwich composite component which does not contain a thermoplasticmaterial.

Document EP 0 894 611 B1 describes a method for producing a componentfor motor vehicles by pressing a panel comprising at least a first and asecond cover layer as well as a cellular core of thermoplastic materialpositioned between them, wherein both cover layers are made ofreinforced thermoplastic material. Additional material reservoirs areformed in regions of shape-induced curvatures, counteracting a localreduction in thickness wherever it occurs.

SUMMARY OF THE INVENTION

The problem addressed by the invention is to further develop a methodfor producing a sandwich composite component with pressed two- orthree-dimensional shape having at least one structured core layer whichis made of thermoplastic material and has two opposite core layersurfaces, each of which is directly or indirectly cohesively bonded to athermoplastic cover layer, in such manner that large-scale manufacturingon an industrial scale is rendered possible, and which further enablesthe production of at least one of a flat and a slightly to moderatelycurved sandwich composite components in specifically predefined regionsof the component, each with a defined core layer height. It shouldfurther be possible to create sandwich composite components of such kindwith a fluid-tight component periphery, whereby the interior structuredcore layer is protected from the external atmosphere. In this way, itshould be possible to produce ready-for-use sandwich compositecomponents in not more than a few minutes, which are consequentlyavailable in large numbers and with a long service life.

The method for producing a sandwich composite component with a pressedtwo- or three-dimensional shape has the following method steps:

The first step is to heat a flat, sandwich semi-finished productcontaining the at least one structured core layer with the cover layersjoined at the core layer surfaces thereof by infrared radiation,preferably contactlessly, so that in the regions that are to be formedoccur with the structured core layer having a temperature lower than amelting point associated with the thermoplastic material of the corelayer, and at least parts of each of the two cover layers have atemperature equal to or higher than a melting point associated with thethermoplastic material of the cover layers. In this way, it is ensuredthat the structure of the core layer can be molded and retain itsstructure during the moulding compression, and both cover layersparticipate in cohesive bonding with the core layer surfaces at the endof molding. The cover layers are each made of a thermoplastic material,which preferably is the same thermoplastic material or a thermoplasticmaterial of the same type as that of the structured core layer. Thisthermoplastic material advantageously has a partly crystallinethermoplastic whose melting temperature constitutes the crystallinemelting temperature. Additionally, the cover layers preferably containstructure-reinforcing endless fiber components with the fiber lengthsmeasuring more than 2 cm, wherein the individual fibers are arrangedhaphazardly or ideally pass completely through the semi-finished productonce and are arranged approximately unidirectionally or are in a wovenstructure in at least one layer. The heating of the cover layers toabove the softening or melting temperature of the thermoplastic matrixalso allows the fiber components to slide inside the softened coverlayers and over the core layer surfaces. In flat semi-finished productregions, where shaping is not intended to take place, it may further beadvantageous not to melt the cover layers.

In a preferred variant, besides the thermoplastic, the core layer alsocontains at least one fill material from the following materials: talcumparticles, chalk particles, glass flour or powder and short fibers madeof the fiber materials listed earlier, each of which are contained inthe cover layers.

Then, the heated, hitherto flat sandwich semi-finished product istransferred into a pressing tool which comprises at least two pressingmold halves which are mounted in linearly movable manner relative toeach other along a spatial axis, of which at least a first pressing moldhalf has at least two pressing mold segments which are mounted inlinearly movable manner relative to each other along a spatialdirection. The warmed sandwich semi-finished product is transferred andinserted in the pressing tool in such manner that the sandwichsemi-finished product comes into surface contact with at least a regionof at least one of the two pressing mould halves. The sandwichsemi-finished product preferably bears or rests on the pressing mouldhalf which is opposite the pressing mould half with the at least twopressing mould segments that are mounted so as to be linearly movablerelative to each other along the spatial direction. In the followingtext, this pressing mold half will be designated the second pressingmold half for purposes of differentiation.

The warmed sandwich semi-finished product is not necessarily butadvantageously positioned and fixed on the surface of the secondpressing mold half by negative pressure. For this purpose, at leastsub-regions of the second pressing mould half are equipped with vacuumsuction elements, which guarantee that the sandwich semi-finishedproduct adheres to the at least one surface of the pressing mold halvesprofoundly and secured reliably against lateral slippage.

In the course of a “first process step”, both pressing mold halves ofthe pressing tool are moved towards each other along the spatialdirection, such that at least regions of the sandwich semi-finishedproduct come into surface contact with both oppositely disposed pressingmold halves, such that a first pressing mould segment runs ahead of therespective other pressing mold segment of the first pressing mold halfin the direction of movement, i.e. the first pressing mold segmentprotrudes beyond the respective other pressing mold segment in thedirection of movement by a distance Δx. In this process, the leadingfirst pressing mold segment comes into surface contact with one of thetwo cover layers, while the respective other cover surface already bearson the opposite, respective other pressing mold half, advantageouslysupported by a vacuum. The further movement of the two pressing moldhalves towards each other causes the warmed sandwich semi-finishedproduct to be pre-pressed in two or three dimensions between the firstpressing mold segment and the second pressing mold half, until a firstminimum spacing is reached between the first pressing mold segment andthe second. In this case, the first minimum spacing corresponds to agreatest thickness which is assignable to the pre-pressed sandwichsemi-finished product. In the case of a honeycomb-like core layer, whosethe honeycomb ridges are preferably orientated parallel to the spatialdirection along which the two pressing mold halves move towards eachother, the honeycomb cell heights, that is the lengths of the honeycombridges are only reduced with a slight increase in the cover layers, andby an amount depending on the tool gap if at all, during the pressingprocess. This first pressing process step in which the sandwich isshaped, without a sharp reduction of the core height may also beperformed in several stages, from the inside outwards by means of amultipart compression mold segment.

The at least one leading pressing mold segment is preferably equippedwith vacuum suction elements, of which the surfaces aligned to facetowards the pressing gap constitute a part of the molding nip.Subsequently, the cover layer surface region which is in contact withthe first, leading pressing mold segment, is preferably sucked andfixedly attached to the first pressing mold segment partly or completelyby negative pressure. Due to the contact on both sides with thepre-pressed sandwich semi-finished product at the opposite contactregions, the sandwich semi-finished product is cooled by contactcooling. This in turn leads to the partial or complete solidification ofthe thermoplastic materials of the contacted cover layer regions at thepreviously melted cover layer surface region. This targetedsolidification and the preferably vacuum-based adhesion of the sandwichsemi-finished product to the leading pressing mould segment have astabilizing effect on these sandwich regions. This stabilization reducesor entirely prevents undesirable deformations in the pre-pressedsandwich semi-finished product during the subsequent, second pressingprocess step.

In the course of the subsequent, second pressing process step, therespective other pressing mold segment of the first pressing mold halfis deflected in the spatial direction onto the opposite, second pressingmold half, while the first pressing mold segment rests relative to theopposite, second pressing mold half, that is the sandwich semi-finishedproduct is not exposed to any further pressing forces in the contactregion with the first pressing mold segment. Through its deflection, therespective other pressing mold segment comes into contact with thepre-molded sandwich semi-finished product directly or indirectlyadjacent to a region that was unaffected by the earlier pre-pressing,until a second minimum spacing is reached between the respective otherpressing mold tool and the second pressing mold half. The second minimumspacing is preferably selected such that the thermoplastic material ofthe cover layers and of the core layer is compacted in his region toform a multilayer laminate. The pressure prevailing in this pressingstep, particularly in the peripheral regions that are to be compactedand the regions of the pre-molded sandwich semi-finished productdirectly adjacent thereto, as well as the high temperatures cause thecover layers to be welded cohesively to the plastic film resulting fromthe core layer.

It is precisely this compacted multilayer laminate as well as thetransition region between the first and second minimum spacings whicheffectively forms a fluid-tight seal for the internal, adjacent,structured core layer.

Depending on the shape of the respective other pressing mold segment andthe nature of its deflection relative to the oppositely arranged secondpressing mold half, a geometrically definable, three-dimensionaltransition contour in the nature of a constant or steep-flankedtransition is formed between the region of the sandwich semi-finishedproduct which was pre-molded with the aid of the first pressing moldsegment and the region of the sandwich composite component which wasfinally molded with the respective other pressing mold segment.

After pressing but before final molding of the component, the shapedsandwich component dwells for a few seconds longer in the pressing toolto allow it to cool down. During this time, the thermoplastic matrix ofall cover layer regions sets fully, and the component temperature fallsgenerally. At this point, the residual negative pressure may be usedadvantageously to reduce air inclusions and improve the surface quality.

In a preferred variant, warming of the flat sandwich semi-finishedproduct takes place by means of infrared radiation in such manner thatthose areas of the sandwich semi-finished product which in the secondpressing process are joined to form a fluid-tight component peripheryand/or undergo greater reduction of the core layer thickness, within theshape transition geometries, for example, are warmed in such a way thatthose regions overheat and lose some thickness or height throughspontaneous melting, in some cases at least one of after the IRradiation heating and before the shaping. Subsequently, this enablesbetter cohesive bond between the cover layer matrix in the three-layerlaminate and the shaped core layer which melted into a plastic film andwas reshaped, as well as less marked buckling of the core ridges inadjacent transition geometries within the core layer.

The method according to the invention may also be combined directly withthermoplastic injection moulding, thus allowing another degree offreedom of form.

A sandwich composite component constructed according to the inventionwith a pressed two- or three-dimensional shape, having at least onestructured core layer that is made of thermoplastic material and has twoopposite core layer surfaces, and which comprises thermoplastic coverlayers, each of which is cohesively bonded directly or indirectly to thetwo core layer surfaces, is characterized by at least onethree-dimensional transition contour, which monolithically connects afirst region of the sandwich composite component, in which thestructured core layer separates the two cover layers from each other, toan adjacent second region of the sandwich composite component, in whichthe structured core layer as a plastic film and both cover layers arecontained, forming a compacted and welded multilayer laminate.

The three-dimensional transition contour, which is preferably embodiedas a steep-flanked or as a flat chamfer, extends around the edge, alonga peripheral circumferential border of the sandwich composite component.In combination therewith or alternatively thereto, it is possible toprovide the transition contour inside the sandwich composite componentin such a way that the first region, in which the structured core layeris contained and separates the two cover layers from each other,surrounds at least a part of the second region.

The sandwich composite component according to the invention may have athree-dimensional deformation in the first region which deviates from aflat surface extension at least in areas thereof, for example in theform of a wavy curvature of the flat composite consisting of thestructured core layer and the two cover layers.

Both cover layers of the sandwich composite component are preferablymade from a thermoplastic material to which endless fiber components,preferably in the form of aramid, carbon, ceramic, glass, quartz orbasalt fibers have been added. The individual fibers are ideallydimensioned and arranged such that they pass once completely through thesandwich semi-finished product and are arranged approximatelyunidirectionally in at least one layer, or they have the form of a wovenstructure.

The sandwich composite component according to the invention maypreferably be used as a load-bearing component in the automotive,caravan, shipbuilding and aircraft construction fields, or as aload-bearing structure for photovoltaic modules or for solar thermalenergy modules or in the sports industry.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, the invention will be described for exemplarypurposes without limitation of the general inventive thought, on thebasis of exemplary embodiments, with reference to the drawing. In thedrawing:

FIGS. 1a )-c) Show sequence images illustrating the shaping of asandwich composite component with structure-receiving core layer andfluid-tight component periphery according to the invention;

FIG. 2 Represents a sandwich semi-finished product with flatconstruction;

FIG. 3a ) Shows a longitudinal section through a finished sandwichcomposite component, and

FIGS. 3b )-g) Show detail views of longitudinal sections.

DETAILED DESCRIPTION OF THE INVENTION

The method according to the invention enables production of a two- orthree-dimensionally shaped sandwich composite component 4 in twoconsecutive process steps using a pressing tool 1 from a flat sandwichsemi-finished product 4′ with a structured core layer 8 and two coverlayers 9 which cover it on both sides within a cycle time from one to afew minutes. The two consecutive process steps for the shaping areinitiated during a linear tool closing movement. The linear closingmovement is performed with the aid of a vertically or horizontallyclosing pressing tool which will be explained below with reference toFIGS. 1a ) to c).

FIGS. 1a ) to c) each illustrate a cross-sectional representationthrough a pressing tool 1 in chronologically successive methodsituations. The pressing tool 1 has two preferably metal pressing mouldhalves 2, 3, which in the closed state enclose a cavity, inside whichthe sandwich composite component 4 to be produced is ultimately formedas illustrated in FIG. 1c ).

The pressing tool 1 is equipped with two deflectable pressing moldhalves 2, 3 which are linearly movable along a spatial direction R,preferably vertically as shown, or horizontally, of which the upper,first pressing mould half 2 as shown comprises two pressing mouldsegments 5, 6 which are mounted in a linearly movable manner relative toeach other along the spatial direction R. The second pressing mold half3 which is positioned opposite the first pressing mould half 2 and isconstructed as a single part in this case.

In the starting situation represented in FIG. 1a ), the first pressingmold segment 6 is deflected relative to the respective other pressingmold segment 5 by a distance Δx and protrudes downwards with respect tothe respective other pressing mold segment 5. Such a configurationenables a two-stage pressing process with interim stabilization of theinitially reshaped geometry.

Vacuum cups, which are preferably made from air-permeable materials suchas porous aluminium, metal foams or sintered metals, are integrated inthe pressing mold segments 5, 6 and on the surface of the lower pressingmold half 3, and are connected to a corresponding negative pressuresource provided on the tool side.

In the situation shown in FIG. 1a ), a flat sandwich semi-finishedproduct 4′ is lying on the surface of the lower pressing mold half 3.

FIG. 2 represents a flat sandwich semi-finished product 4′ of such kind,which has a structured core layer 8 and two cover layers 9, 10 are eachmade from the same thermoplastic material. The core layer 8 has astructured construction in the form of honeycombs or cylinders arrangedside by side. The cover layers 9, 10 contain endless fibers for thepurpose of reinforcement, wherein the individual fibers ideally passentirely through the semi-finished product once and are arrangedunidirectionally in at least one layer or are provided in the form of awoven structure.

The sandwich semi-finished product 4′ represented in FIG. 2 is broughtto a certain thermal state before or while it is placed in the pressingtool 1. The defining feature this thermal state is that thethermoplastic material of the cover layers 9 and 10 reaches temperaturesabove its melting temperature, and the thermoplastic material of thecore layer 8 reaches temperatures equal to or below its meltingtemperature. Heating of the sandwich semi-finished product 4′ preferablytakes place immediately before the shaping with the aid of infraredradiation warming applied to both sides.

The two-stage pressing process begins with a closing movement of thepressing tool 1, in which the first pressing mould half 2 is deflectedrelative to the second pressing mould half 3, in the present casevertically downwards. The sandwich semi-finished product 4′ is attachedat least to the underside thereof before and during the shaping byvacuum cups.

FIG. 1b ) represents the situation in which the upper pressing mold half2 has been lowered vertically, and the originally flat sandwichsemi-finished product 4′ has been pre-shaped by contact with the leadingfirst pressing mold segment 6 with the application of pressing force.Pre-pressing of the sandwich semi-finished product 4′ was carried outwhile preserving the structure of the core layer 8. This shaping processfor obtaining the pre-shaped sandwich semi-finished product 4″illustrated in FIG. 1b ends when a minimum spacing 11 between pre-shapedsandwich semi-finished product 4″ is reached. The first minimum spacing11 corresponds to a maximum layer thickness of the pre-pressed sandwichsemi-finished product 4′. Preferably, all contact regions close to thesubsequent transition contour between the cover layers 9, 10 of thesandwich semi-finished product 4′ and the surfaces of the first pressingmold segment 6 as well as the second pressing mold half 3 are suppliedwith negative pressure during the pre-pressing, with the result that theeffect of the negative pressure on the contact regions between sandwichsemi-finished product 4″ and pressing mold tool 1 serves to prevent atleast one of core failure and undesirable core height reduction of thecore layer 8.

In the time before a second, subsequent pressing process step is carriedout, the pre-shaped sandwich semi-finished product 4″ is stored andcooled inside the pressing mould segment 6 which is in contact with thesandwich semi-finished product 4″ and the pressing mould half 3 withoutany further molding forces that would modify the shape of the pre-shapedsandwich semi-finished product 4″. The sandwich semi-finished product iscooled by contact cooling through contact on both sides of thepre-pressed sandwich semi-finished product 4″ on the opposite contactregions. This brings about partial to total solidification of thethermoplastic material of the contacted cover layers at the previouslymelted cover layer surface regions. This targeted solidification and theadhesion of the sandwich semi-finished product 4″ to the leadingpressing mold segment 6 is preferably due to negative pressure havingthe effect of stabilizing these sandwich regions. The stabilizationreduces or entirely prevents undesirable deformations on the pre-pressedsandwich semi-finished product in the subsequent, second pressingprocess step. The duration of this stabilizing state is at least 1second.

In a second pressing process step, the previously uncontactedsub-regions of the sandwich semi-finished product 4″ are reshaped andpressed by deflection of the respective other pressing mold segment 5against the opposite second pressing mold half 3, while the firstpressing mold segment 6 rests relative to the second pressing mold half3. As the closing movement progresses, the sandwich core is compressedin the regions laterally outside the first pressing mold segment 6 untila second minimum spacing 14 is reached between the respective otherpressing mold segment 5 and the second pressing mold half 2, thusforming a compacted laminate 12. These compacted component regions 12may be molded to extend around the periphery of at least one of thecomponent and in the interior of the sandwich component depending on thecomponent shape and the design of the pressing mold segments (5, 6).

The transition 13 between the structurally preserved core layer regionsand the peripheral compacted laminate region 12 may have a steep-flankedor be constant depending on the construction and shape of the pressingmold segments.

The pressing method explained here may be combined with otherconventional processing steps according to the pressing tool used oreven the injection molding machine used, such as for example asubsequent edge trimming with punches or further functionalization byinjection molding.

The sandwich composite components produced with the method according tothe invention may include both flat and curved sandwich regions withdefined core height. The core height depends in each case on the gapwidth inside the cavity as illustrated in FIG. 1c ).

The transition 13 between regions in which the sandwich compositecomponent 4 is shaped with a core layer whose structure is preserved andthe adjacent compacted laminate regions 12 may be shaped as a chamfer,for example.

After the pressing and before the final molding of the component, theshaped sandwich component dwells in the pressing tool for a few secondslonger in order to cool down. In this time, the thermoplastic matrix ofall cover layer regions solidifies, and the component temperaturegenerally cools down. In this situation, the remaining negative pressuremay be used advantageously to reduce air inclusions and improve thesurface quality.

The compacted laminate which extends circumferentially around theperiphery of the component, may seal the interior of the sandwichagainst penetration by air and fluids, and at the same time may serve asa joint. It is also possible to create compact laminate regions as withcorresponding transitions inside the finished sandwich compositecomponent 4.

FIG. 3a ) shows a longitudinal section through a finished sandwichcomposite component 4, which besides a peripheral compacting 12, inwhich both cover layers 9, 10 are pressed jointly with the core layer 8to form an integral or practically integral material composite, containsthe transition region B1, an unshaped region B2 adjacent thereto, andsubsequently a 2D- and 3D-shaped region B3.

The transition region B1 is illustrated in detail in FIGS. 3b ) and 3c), of which FIG. 3b ) is a photographic detail representation showingboth cover layers 9, 10 and the structure walls of the core layer 8arranged between them, and FIG. 3c ) shows a schematic partiallongitudinal section in which the respective lower half of thelongitudinal section is shown in the transition region B1. FIGS. 3d )and e) show corresponding illustrations for the unshaped region B2, andFIGS. 3f ) and g) for the shaped region B3.

The preferably honeycomb-like core layer 8 includes structure walls 15,whose opposite structure wall edges are each cohesively joined to one ofthe two cover layers 9, 10 wherein a material accumulation 16 ofthermoplastic material in similar to a weld bead is provided on eachside of the structure wall borders, each of which is joined to a coverlayer 9, 10, the accumulation being bonded integrally with both thecover layer 9, 10 and the structure wall 15.

In transition region B1, the structure wall height becomes lower,starting from the unshaped structure wall height h in region B2 andprogressing downwards, forming a complete film structure with the coverlayers 9, 10 in the edge region of the compacting 12. Due to the heightreduction caused by pressing forces and the maximum temperatures in thestructure walls 15 close to the cover layers 9, 10 and the cover layers9, 10 themselves, which are hotter than the melting temperature of thethermoplastic matrix, the structure walls 15 begin to deform, at leastin the region close to the cover layers 9, 10 and themselves melt intothe weld-bead like material accumulation. This results in a strongerweld-bead like material accumulation with further reduction of thestructure wall height h. Moreover, shearing forces lead to a deformationof the material accumulations 16 tangentially to the cover layers 9, 10relative to the structure wall 15 in each case. Foot-like deformations16′ are formed, from which the structure walls 15 extend.

The structure walls 15 extend substantially linearly between the twocover layers 9, 10 within the unshaped sandwich composite componentregion B2. Weld bead-like material accumulations 16 of thermoplasticmaterial are located on both sides of each of their structure wallborders, and are each bonded monolithically in these regions with boththe cover layers 9, 10 and the structure walls 15.

Inside the region B3 of the sandwich composite component 4 with apressed two- or three-dimensional shape, the weld bead-like materialaccumulations 16 of thermoplastic material exhibit a shear force-induceddeformation which extends unidirectionally with the adjacent cover layersuch that an increasing material accumulation 16′ forms on one side ofthe structure wall borders depending on the curvature, as may be seenparticularly clearly in the detail illustrations of FIGS. 3f ) and g).Ideally, the structure walls 15 are largely unshaped, that is straight,in this region B3 as well. However, deviating structure walldeformations may occur, caused by excessively steep curvatures of thesandwich composite component 4, too rapid reduction of the structurewall height h in regions B2 and B3 and/or by the temperature being toolow in the cover layers 9,10, which then results in blockage of thesliding motion from the cover layers 9,10 on the structure walls 15 andtherefore results less in shear-induced deformation of the weld-beadlike material accumulations 16, but instead to a shear-induceddeformation of the structure walls 15 themselves. Insufficient highcover layer temperatures are attributable to inadequate thermal energyinput during the heat treatment with at least one of IR radiation andexcessively long transfer time from the time of completion of the IRradiation heat treatment to the start of the first pressing processstep.

LIST OF REFERENCE NUMERALS

-   1 Pressing tool-   2 First pressing mould half-   3 Other pressing mould half-   4 Sandwich composite component-   4′ Flat sandwich semi-finished product-   4″ Pre-pressed sandwich semi-finished product-   5 Respective other pressing mould segment-   6 First pressing mould segment-   7 Flat sandwich semi-finished product-   8 Core layer-   9, 10 Cover layer-   11 First minimum spacing-   12 Compacted layer composite-   13 Transition-   14 Second minimum spacing-   15 Structure wall-   16 Material accumulation-   16′ Single-sided material accumulation-   B1 Transition region-   B2 Unshaped region-   B3 Shaped region

1-21: (canceled)
 22. A method for producing a sandwich compositecomponent with a pressed two- or three-dimensional shape, having atleast one structured core layer made of a thermoplastic material whichhas two opposite core layer surfaces, and with thermoplastic coverlayers cohesively bonded with each of the two core layer surfaces,comprising: heating a flatly shaped sandwich semi-finished product whichincludes the at least one structured core layer with the cover layersbonded to each side of the core layer surfaces thereof by infraredradiation heating, so that the structured core layer has a temperaturebelow a melting temperature associated with the thermoplastic materialof the core layer, and at least parts of the two cover layers have atemperature equal to or above a melting temperature associated with thethermoplastic material of the cover layers; transferring the heated,flat sandwich semi-finished product into a pressing tool comprising atleast two pressing mold halves which are mounted in a linearly movablemanner relative to each other along a spatial direction with at leastone first pressing mold half including at least two pressing moldsegments which are mounted in a linearly movable manner relative to eachother along the spatial direction so at least regions of the sandwichsemi-finished product come into surface contact with at least one of thetwo pressing mold halves; moving the pressing mold halves towards eachother along the spatial direction so that at least some regions of thesandwich semi-finished product are brought into surface contact with theat least two pressing mold halves so that a first pressing mold segmentruns ahead of the respective other pressing mold segment of the firstpressing mold half in the direction of movement, a region thereof cominginto contact with one of the two cover surfaces, and together with theother pressing mold half pre-presses the sandwich semi-finished productin two or three dimensions, until a first minimum spacing correspondingto a greatest thickness assignable to the pre-pressed sandwichsemi-finished product is reached between the first pressing mold segmentand the other pressing mold half; stabilizing the pre-shaped sandwichsemi-finished product within the regions contacted by at least one ofthe first pressing mold segment and the other pressing mold half by acontact cooling process; and deflecting the other pressing mold segmentof the first pressing mold half in the spatial direction onto the otherpressing mold half, while the first pressing mold segment rests relativeto the other pressing mold half, and contacting some regions of thepre-pressed sandwich semi-finished product and completing molding untila second minimum spacing is reached between the other pressing moldsegment and the other pressing mold half, with spacing being selected tobe smaller than the first minimum spacing to obtain the sandwichcomposite component pressed into a two- or three-dimensional shape. 23.A method according to claim 22, wherein: the flat sandwich semi-finishedproduct has one of a honeycombed or cylindrically structured core layer.24. A method according to claim 23, wherein: the cover layers are each athermoplastic material, from which the core layer is also produced, andto which structure-reinforcing fiber components have also been added.25. A method according to claim 24, wherein: the structure-reinforcingfiber components are endless fibers, wherein individual fibers passcompletely through the sandwich semi-finished product once and arearranged approximately and unidirectionally in at least one layer or ona woven structure.
 26. A method according to claim 22, wherein: theheating of the flat sandwich semi-finished product is performedcontactlessly by an infrared radiation heating process.
 27. A methodaccording to claim 22, the contacting of the sandwich semi-finishedproduct with at least one pressing mold half and the first pressing moldsegment is supported by application of a negative pressure to contactregions between the sandwich semi-finished product and the pressing moldhalves, and the sandwich semi-finished product is cooled in the contactregion with the pressing mold tool by a contact cooling process.
 28. Amethod according to claim 22, wherein: the movement of the two pressingmold halves and the two- or three-dimensional pressing associatedtherewith toward each other to obtain the pre-pressed sandwichsemi-finished product which is carried out with the structured corelayer being retained in a pre-shaped sandwich semi-finished productwhich preserves the structure.
 29. A method according to claim 22,wherein: the movement towards each other of the two pressing mold halvesand the two- or three-dimensional pre-pressing to obtain the pre-pressedsandwich semi-finished product constitutes a first pressing process stepwhich is followed by a second pressing process step, in which therespective other pressing mold segment of the first pressing mold halfis deflected in spatial direction onto the other pressing mold half, andthe pre-pressed sandwich semi-finished product is contacted directly orindirectly adjacent in a region excluded from the pre-pressing, and thepre-pressed sandwich semi-finished product is compacted in this regionby the application of a pressing force to a thickness which correspondsto the second minimum spacing.
 30. A method according to claim 22,wherein: the second minimum spacing is selected so that thethermoplastic material of the cover layers and the core layer is formedof a compacted material composite in a region of the sandwich compositecomponent which was finally molded by the pressing mold segment.
 31. Amethod according to claim 22, wherein: the deflection of the respectivethe other pressing mold segment of the first pressing mold half isperformed so that a geometrically definable three-dimensional transitioncontour is formed with either a constant or an inclined transitionbetween a region of the pre-pressed sandwich semi-finished productcreated with the first pressing mold segment and a region of thesandwich composite component which was finally molded by respectiveother pressing mold segment.
 32. A method according to claim 29,wherein: after the first pressing process step the pre-shaped sandwichsemi-finished product is cooled inside regions contacted with at leastone of the first pressing mold segment and the other pressing mold half.33. A method according to claim 32, wherein: during the cooling and asolidification of the thermoplastic material resulting therefrom, thepre-shaped sandwich semi-finished product is fixed on the contactregions to the first pressing mold segment and to the other pressingmold half by means of negative pressure.
 34. A method according to claim22, wherein: the stabilization is carried out free from molding forcesacting on the pre-shaped sandwich semi-finished product for a period ofat least 1 second.
 35. A sandwich composite component with a pressedtwo- or three-dimensional shape, which has at least one structured corelayer made of thermoplastic material with two opposite core layersurfaces, and with thermoplastic cover layers which are each bonded withthe two core layer surfaces, wherein at least one three-dimensionaltransition contour is provided, which connects a first region of thesandwich composite component, in which the structured core layerseparates the two cover layers from each other, with an adjacent secondregion of the sandwich composite component has a single part, in whichthe structured core layer and both cover layers are compacted and weldedwith a material bond to form a multilayer laminate.
 36. A sandwichcomposite component according to claim 35, wherein: thethree-dimensional transition contour is positioned on at least one of anedge, along a peripheral circumferential border of the sandwichcomposite component and an inside the sandwich composite component sothat the first region at least partially encloses the second region. 37.A sandwich composite component according to claim 35, wherein: coverlayers are each a thermoplastic material, from which the thermoplasticmaterial core layer is also made, and to which additionalstructure-reinforcing fiber components are added.
 38. A sandwichcomposite component according to claim 37, wherein: thestructure-reinforcing fiber components include endless fibers, withindividual fibers passing completely through the sandwich semi-finishedproduct once and are arranged unidirectionally at least in one layer orare present in a woven structure.
 39. A sandwich composite componentaccording to claim 35, wherein: the structured core layer of the flatsandwich semi-finished product has structure walls with oppositestructure wall edges bonded with one of the two cover layers; and a weldbead of thermoplastic material is on each side of each of the structurewall edges bonded to a cover layer, which is bonded integrally both withthe cover layer and with the structure wall.
 40. A sandwich compositecomponent according to claim 39; wherein: in regions of the sandwichcomposite component with a pressed two- or three-dimensional shape wherea shape has been changed, the weld bead of thermoplastic materialaccumulates which has a shear force induced deformation extendingunidirectionally with an adjacent cover layer.
 41. A sandwich compositecomponent according to claim 39, wherein: in regions of decreasingstructure wall height of the sandwich composite component having apressed two- or three-dimensional shape where shape has been changed,the structure walls have curved sections adjacent to structure walledges.
 42. A method of use of the sandwich composite component accordingto claim 22 as a flat, load-bearing component or a load-bearingstructure.